Title of Invention

A METHOD FOR FORMING MOLDS AND A CORE FOR CASTING METAL

Abstract A method of forming a mold which scarcely emits any gas having a harmful effect on human body even upon binder heating; and a core for metal casting are disclosed. More particularly, there is provided a method of forming a mold which comprise agitating an aggregate mixture composed of granular aggregate, a water soluble binder and water so as to foam the aggregate mixture, charging the foamed aggregate mixture in a space for mold formation and evaporating water to thereby solidify the aggregate mixture, and there is further provided a core for metal casting. In one embodiment, a cross linking agent can be added so that curing can be effected before or after taking our of the mold from the space for mold formation.
Full Text Specification
Title
A method for forming molds and a core for casting metal
Field of the Inventions
[0001] The present inventions are related to a method for forming molds by which little
gas with discomforting odors and bad effects on human bodies is generated while
binders are heated when materials for forming molds that include binders are formed
and when melted metal is poured using a core for casting formed of materials for
forming molds that include binders, and to a core for casting metal produced by the
method for forming molds. Further, the present inventions are related to an aggregate
material mixture for forming molds using the method for forming molds of the
inventions.
Background of the Inventions
[0002] Phenol resins are used as caking additives in Example 1 of the method for
forming molds shown in the Official Gazette of Japanese Patent Early-publication
(Kokai) No. Hei. 05-32148, and volatile gases such as formaldehyde, phenol and
ammonia are generated when binders are cured by the heat of formed dies. The
gases generated cause discomforting odors and have bad effects on human bodies.
Or water glasses are used as in Example 2, and it is not preferable that molds after
casting become refuse, because they cannot be recycled.
[0003] Also, a so-called forming method for shell molds, in which sand coated with
binders is blown and filled in heated dies for forming and the filled binders coated
with sand are cured by the heat of the dies, is disclosed in the Official Gazette of
Japanese Patent Early-publication {Kokai) No. Hei. 10-193033.
[0004] Volatile gases such as formaldehyde, phenol, and ammonia are generated when

binders are cured by the heat of the dies in the method for forming shown in the
references of the patent. The gases generated cause discomforting odors and have
bad effects on human bodies. Also, when these dies are used for casting, for example,
aluminum alloys and resin binders are not fully volatilized or decomposed, because
the pouring temperature into molds is about 700 °C. As a result, a core may not be
easily removed from cast metal after the cast metal is cooled. Further, a water
jacket core for producing aluminum castings for automobile engines is complicated
in shape and is very thin. Thus, if the binders in the core are not completely baked
and decomposed by the heat conduction from the poured and melted metal, it is
difficult to remove the core sand from the castings.
[0005] Further, as shown in the Official Gazette of Japanese Patent Early-publication
(Kokai) No. Sho. 59-47043, it is not preferable that a caking additive composition
using multi-functional aldehyde, glyoxal, urea, etc., as cross linking agents be used
for casting, because they may generate toxic gases such as formaldehyde.
[0006] Also, it is very difficult to continuously fill mixtures in a blow head into
molds by the method for forming molds shown in the Official Gazette of Japanese
Patent Early-publication (Kokai) No. Sho. 55-8328, because the unit particles of
silica sand in the blow head aggregate to become bulky because of the method when
casting sand that is combined with binders mainly composed of water and aqueous
binders frozen and the frozen mixture is blow-filled into molds or during the period
that lasts until the second blow-filling is done. Thus, these kinds of methods for
forming molds have not been practically used.
[0007] Further, when a core for casting using aqueous binders is left under a high
humidity, the core may be deformed, and not maintain its shape because the
aqueous binders generally absorb water and their bonds are weakened. There has
been a problem in that water vapor is generated when the water component is
heated and it induces bubbles when pouring metal, though the poured metal can be
used for casting.
[0008] Disclosure of the Inventions
The present inventions were accomplished based on the above problems. First, the
inventions provide a method for forming molds which generates little gas with
discomforting odors or bad effects on human bodies while binders are heated when
materials for forming molds, including binders, are formed and when casting metal is
poured using a core for casting formed of materials for forming molds, including binders,
and provide a core produced by the method for forming molds.
[0009] Second, the inventions provide, the method for forming molds by which an
aggregate mixture including binders and sand can be fully filled in detailed parts in a
space for forming molds and a core produced by the method for forming molds.
[0010] Also, third, the inventions provide a core for casting metals which can be easily
removed after poured and melted metal is cooled. Namely, the inventions provide a
core for casting metals in which binders are volatilized or decomposed by the heat of
poured and melted metal and which can be easily removed after the poured and melted
metal is cooled. When nonferrous alloys, for example, aluminum alloys, are used for
the core, the pouring temperature into molds is about 700 °C and below the pouring
temperature of iron - system materials, of about 1400°C.
[0011] Fourth, the inventions provide a method for forming molds by which a core for
casting metals formed of an aggregate material mixture that includes sand and binders
can maintain its shape under high humidity and provide a core produced by this method
for forming molds.
[0012] Fifth, the inventions provide a core for metals such as iron - system metals,
copper alloys, etc., of which the pouring temperatures are higher than those for
aluminum alloys.
[0013] In one embodiment, the inventions provide a method for forming molds
characterized in foaming an aggregate material mixture by stirring an aggregate
material mixture composed of granular aggregate materials, aqueous binders and water,
filling the foamed aggregate material mixture into a space for forming molds,
evaporating the water component in the aggregate material mixture, caking the
aggregate material mixture, forming molds, and then taking out the formed mold from
the space for forming molds.
[0014] In another embodiment, the inventions provide a method for forming molds
characterized in foaming an aggregate material mixture by stirring an aggregate
material mixture composed of granular aggregate materials, aqueous binders, cross
linking agents tnat induce a cross linking reaction with the aqueous binders and water,
filling the foamed aggregate material mixture in a space for forming molds, then taking
out the formed mold from the space for molding molds after evaporating the water
component of the aggregate material mixture in the space for forming molds and
causing a cross linking reaction with the aqueous binders and the cross linking agents.
[0015] In another and further embodiment, the inventions provide a method for forming
molds characterized in foaming an aggregate material mixture by stirring an aggregate
material mixture composed of granular aggregate materials, aqueous binders, cross
linking agents inducing a cross linking reaction with the aqueous binders and water,
filling the foamed aggregate material mixture in a space for forming molds, taking out
the formed mold from the space for forming molds after evaporating the water
component of the aggregate material mixture in the space for forming molds, and
causing a more complete cross linking reaction with the aqueous binders of the formed
mold that has been taken out.
[0016] Also, the inventions provide a core produced by the method for forming molds of
the inventions.
[0017] Further, the inventions provide an aggregate material mixture for forming molds
preferable for the use in the method for forming molds of the inventions. The
aggregate material mixture for forming molds is characterized in being foamed to be a
whipped cream in which granular aggregate materials are equally dispersed.
[0018] Brief Description of the Accompanying Drawings
[Figure 1] Figure 1 shows the foamed aggregate mixture foamed by stirring.
[Figure 2] Figure 2 shows a longitudinal front elevation view of an apparatus for
forming molds for carrying out the inventions. Mark 1 shows a mixture, Mark 2 shows
a cylinder, Mark 3 shows a die for forming molds, and Mark 4 shows a cavity in the
Figure.
[Figure 3] Figure 3 shows the results of the analyses of the components of gases
generated from the binders of the inventions by a mass spectrometer.
[0019] Preferable Embodiments for Carrying Out the Inventions
The method for forming molds of the inventions is characterized in having a process of
mixing granular aggregate materials, one or more kinds of aqueous binders (further
adding cross linking agents according to the case) and water, a process of foaming an
aggregate material mixture by stirring an aggregate material mixture, a process of
filling the foamed aggregate material mixture in a space for forming molds, a process of
evaporating the water component in the mixture, caking the aggregate and forming
molds, a process taking out the formed mold from the space for forming molds, and
according to the case a process of causing a cross linking to occur before or after the
process of taking out.
[0020] The granular aggregate materials in the inventions consist of more than one
material chosen from silicate sand, aluminum sand, olivin sand, chromite sand, zircon

sand, mullite sand, and various kinds of artificial aggregate materials, etc.
[0021] The one or more kinds of aqueous binders in the inventions are caking additives
which may be caked by evaporating the water component and contain saccharides and
resins etc.
[0022] Also, it is preferable to use the aqueous ones at ordinary temperature. The
aqueous binders which are aqueous at ordinary temperature can be mixed without
heating the aqueous binders and water when producing the aggregate material mixture
with adding water. But the aqueous binders insoluble in water cannot be mixed with
water without heating.
[0023] However, the aqueous binders which cannot be mixed with water can also be
used if they would be aqueous in the water in the situation wherein they are cooled to
ordinary temperature after they are mixed with water.
[0024] In the inventions, a core can be easily removed from poured and melted metal
because the binders are easily volatilized and decomposed when melted metal is poured
in the core produced by the method for forming molds of the inventions by using the
aqueous binders.
[0025] As the aqueous binders used for the inventions, one or more kinds with a
saponification degree of 80 - 90 mole % of polyvinyl alcohols or their derivatives, starch
or its derivatives, saponins, or saccharides, are preferable. Those of which the degree of
saponification is more than 95 mole % and not more than 99 mole %, and are soluble in
hot water, can also be used. Here, a saponification degree of 80 - 95 mole % of
polyvinyl alcohols or their derivatives, alpha — starch, dextrin or their derivatives,
saponins, or sugar, are soluble in water at ordinary temperature. Specific examples of
polyvinyl alcohol derivatives are polyvinyl alcohols having acetic acid groups, carboxyl
groups, lactic acid groups, silanol groups, etc. Specific examples of starch are alpha -
starch and dextrin derived from potato, corn, tapioca, and wheat, etc. Specific examples
of starch derivatives are etherilificated, esterificated, and cross-linked starches. The
aqueous binders used for the inventions are easy to obtain, and, in particular, alpha -
starch and dextrin are cheap. Also, the saccharides include poly - saccharides, di -
saccharides, and mono - saccharides. In the specification the term "poly - saccharides"
includes any vegetable poly - saccharides soluble in water at ordinary temperature (but,
they do not include cellulose).
[0026] The content of the soluble binders is preferably 0.1 - 5.0 weight parts compared
to 100 weight parts of aggregate materials. Formed molds having enough strength
cannot be obtained with less than 0.1 weight parts of aqueous binders. Molds obtained
show excess strength with more than 5.0 weight parts of aqueous binders. Also, as the
binders of the inventions, polyvinyl alcohols and saponins are superior from the point of
easily foaming and starches and saccharides are superior from the point of not
generating discomforting odors. So formed molds are practically done with the proper
arrangement of the ratio by which they [their contents] are combined.
[0027] In the method of containing cross linking agents in an aggregate material mixture,
while adding more cross linking agents according to the case, and causing cross-linking
of the cross linking agents and aqueous binders in the inventions, cross linking reactions are
enhanced by heating the cross linking agents. Thus, the bonds between the granular
aggregate materials of the aqueous binders are strengthened, the reactions between the
aqueous binders and water molecules hardly occur, and molds formed of the aggregate
materials can sufficiently maintain their properties even in high humidity.
[0028] The cross linking agents used in the inventions are- compounds having
carboxylic groups which cross-link by means of ester-bonding, such as oxalic acid,
maleic acid, succinic acid, citric acid, and butanetetracarboxylic acid; ana compounds
which would have carboxylic groups in an aqueous solution, such as methylvinylether-
maleic anhydride copolymers and isobutylene - maleic anhydride copolymers. Also, as
the cross linking agents used in the inventions, those cross linking agents that bond
with ester-bonding generate little toxic gases during the formation of molds or pouring
melted metal, that is, the cross linking agents having carboxyl groups are preferable.
[0029] The amount of the cross linking agents added to be used in the inventions is at
least 5 weight % versus aqueous binders, and preferably 5 - 300 weight %. If the
amount of the cross linking agents versus aqueous binders is less than 5 weight %, the
effect by the cross-linking is not enough, and the formed mold cannot maintain enough
strength under high humidity. Also, if the amount of the cross linking agents versus
aqueous binders is more than 300 weight %, the effect is not different from that of 300
weight %, so the addition of more than an amount of 300 weight % of the cross linking
agents is not economical, and is unpreferable.
[0030] The cross linking agents are used as aqueous solutions in the inventions and
preferably used as more than 5 weight % concentrations of aqueous solutions when, for
example, butanetetracarboxylic acid, citric acid and methylvinyl ether - maleic
anhydride are usecL
[0031] The cross linking reaction of the inventions can be carried out either before or
after taking out formed molds from a space for forming molds. When the cross linking
reaction is carried out after taking out formed molds from the space for forming molds,
the reaction would be done at higher temperatures for shorter times, as for example,
under the atmosphere at 220°C for about 20 minutes and under the atmosphere at
250 °C for about 10 minutes.
[0032] The process of the inventions in which the mixture containing granular
aggregate materials, one or more kinds of aqueous binders (cross linking agents are
added according to the case) and water, is carried out using, for example, a stirrer.
[0033] In the method for forming the molds of the inventions, in the process of foaming
by stirring, the mixture of the aggregate materials is stirred so that foaming air would
be equally dispersed, preferably with the foaming ratio of 50 - 80 %. Foaming is bad
with a foaming ratio of 50 %, and the strength is not sufficient with a foaming ratio of
not less than 80 %. According to this, the effect for the aggregate material mixture to
flow when it is filled under pressure into the space for forming molds is obtained (P'igure
l). The granular aggregate material mixture is equally dispersed as a whipped cream by
this foaming. In the description of the inventions, "foaming" means the period of 10
seconds occurring after the stirring procedure stops, which preferably occurs in the
aggregate material mixture when it is stopped for more than 15 seconds with a foaming
ratio of 50-80%.
[0034] Here, the ratio of foaming was calculated by the following formula.
Ratio of Foaming_ (%) = { (Total Volume of the Mixture) — Volume of Granular
Aggregate Material, Aqueous Binder, and Water}/(Total Volume of the Mixture) } X
100
[0035] Further, the stirring for foaming may be done either by the same stirrer as that
for mixing or by another stirrer. The foamed air generated by stirring is equally
dispersed in the mixture.
[0036] In the present inventions, the method for filling the foamed aggregate material
mixture in the space for forming molds may be by either the method of placing the
foamed aggregate material mixture in a cylinder and pressing it directly or the method
of pressing by air.
[0037] Here, "pressing it directly by a cylinder" means pressing the mixture in the
cylinder (means for storing the mixture) into a die by the manner of press fitting of the
direct pressing by the press fitting of the piston with a pressing mechanism. "Pressing
by air" means the method of supplying compressed air (air) to the upper surface of the
mixture in the means for storing the mixture when press fitting the mixture into a die
with a cover, which cover airtightly closes the opening at the top of the means for
storing the mixture and is connected to a compressed air source provided at the bottom
of the piston rod of the cylinder with the pressing mechanism, instead of the piston in
the method of press fitting the mixture in the means for storing the mixture by the
piston with the pressing mechanism.
[0038] In the process of evaporating a water component in the filled aggregate material
mixture, caking the aggregate material mixture, and forming molds by the method for
forming molds of the present inventions, the method of evaporating the water
component consists of evaporating the water component by a die, set at a high
temperature, which defines the space for forming molds, radiating heated water vapor
or microwaves, leaving the mold in the vacuum atmosphere, and ventilating the space
for forming molds according to the needs, etc.
[0039] In evaporating at a high temperature the water component by a die that
defines the space for molding molds, dispersed bubbles in the aggregate material
mixture and the water component in the binders gather in the central part of the molds
by means of stirring by the heat of the heated die, so molds of which the central part is
low in the density of the packed aggregate materials are obtained. If the mold is used
for casting, it becomes easy to eject the gases etc. derived from the decomposition of the
binders because the amount of the binders is small because of the low density of the
central part and because the part of the hole of the mold is large.
[0040] The cores for casting metal of the present inventions are obtained from forming
by the method for forming molds. When the aqueous binders used in the present
inventions are used for casting nonferrous metal alloys such as aluminum alloys or
magnesium alloys to form a core for casting, the core is easily removed after the binders
are volatilized or decomposed and the poured and melted metal is cooled, though the
pouring temperature in the mold is about 700 °C and a lower pouring temperature
than the pouring temperature of iron- system materials of 1400 °C.
[0041] Also, when the core for casting of the present inventions is used for casting
iron-system metals, normal poured and melted iron-system metal is made by coating
the surface of the core. And a mold can also be ejected and removed.
[0042] Further, in the core for casting metal of the present inventions, the gases
generated during the production and usage of the core for casting metal substantially do
not have discomforting odors, but have the odor of baking biscuits.
[0043] Also, for the preservation of the binder solutions when cross linking agents are
used, preferable is keeping separately two kinds of polyvinyl alcohols or their
derivatives and the other binders, and mixing both of them at the time of use.
[0044] Examples
The method for forming molds of the present inventions is specifically explained in the
following.
[0045] (Process of mixing and stirring l)
To granular aggregate material of 100 weight parts and aqueous solutions comprising a
binder component of 0.1 - 5.0 weight parts in relation to this granular aggregate
material is added water, of which the weight parts and the weight parts of the aqueous
binders are 1-20 weight parts. They are stirred by a stirrer to foam the aggregate
material mixture at the ratio of foaming of 50 - 80%.
[0046] (Process of mixing and stirring 2)
To granular aggregate material of 100 weight parts, aqueous solutions comprising a
binder component of 0.1 - 5.0 weight parts in relation to this granular aggregate
material, and more than 10 weight % of an aqueous solution of 5 - 100 weight % of cross
linking agents in relation to the aqueous binders, is added water of which the weight
parts, the weight parts of the aqueous binders, and the weight parts of the aqueous
solution of the cross linking agents, are 1-20 weight part. They are stirred by a stirrer
to foam the aggregate material mixture at a ratio of foaming of 50 - 80 %.
[0047] (Process of casting)
Next, a process of forming is explained based on Figure 2. The mixture 1 obtained in the
process of mixing and stirring is input into a cylinder 2. Then the cylinder 2 is
extended, the aggregate material mixture 1 is filled in a cavity 4 of a die for forming
molds 3, which cavity is set up at the upper part of the cylinder 2 and is maintained at
200 - 280 °C, a water component of the filled aggregate material mixture is evaporated
and caked, and a formed mold is taken out from the cavity 4 of the die for forming molds
3 after a cross linking reaction has taken place. Or, when the cross linking reaction in
the die for molding molds 3 is not sufficient, the formed mold that is taken out is put in
an incubator maintained at a temperature wherein the aqueous binders and cross
linking agents cause a sufficient cross linking reaction, preferably at 200 — 300 °C for a
time sufficient for the cross linking reaction, preferably for 10 - 40 minutes. Then the
formed mold is taken out from the incubator after a sufficient cross linking reaction has
taken place.
[0048] Example 1
Silica sand (Fluttery Sand) of 100 weight parts, polyvinyl alcohol of (JP - 05: Nihon
Sakubi - Poval) of 0.2 weight parts, starch (DextrinNSD - L: Nisshi) of 0.8 weight parts,
citric acid (Fuso Kagaku) of 0.2 weight parts, and water of 5 weight parts, are mixed
with stirring, foamed at 200 rpm for about 3 minutes by a mixer (Aikousha Desktop
Mixer), and the results of the ratio of foaming of the aggregate material mixture
measured. The results according to the other conditions are shown in Table 1. Also, a
CCD photo of the aggregate material mixture of Test No. 1 is shown in Figure 1.
[0049] Bubbles are equally and sufficiently distributed in the aggregate material
mixture shown in Figure 1. Also, the aggregate material mixture of the conditions of
Test Nos. 1 - 7 in Table 1 (hereafter, the explanation refers to Figure 2) are put in the
cylinder 2, filled with pressure to about 70 cm3 of the volume of the cavity 4, which is
maintained at 250 ºC by an electric cartridge heater of a die 3 for forming molds in a
cylinder, and at a surface pressure of 0.5 MPa of an air cylinder, retained for 2 minutes,
the water component of the aggregate material mixture is evaporated and caked, and
then the formed mold is taken out from the cavity 4 of the die for forming molds 3 to
obtain a formed mold which can be sufficient for its use.
[0050] Example 2
Silica sand (Fluttery Sand) of 100 weight parts, polyvinyl alcohol (JP — 05: Nihon
Sakubi - Poval) of 0.2 weight parts, starch (DextrinNSD - S: Nichiden Kagaku) of 0.8
weight parts, butanetetracarboxylic acid (Rikacid BT - W: Shinnihon Rika) of 0.2
weight parts, and water of 5 weight parts, were mixed with stirring, foamed at about
200 rpm for about 3 minutes by a mixer (Aikousha Desktop Mixer) (hereafter, the
explanation refers to Figure 2), about 80 g of the aggregate material mixture was put in
the cylinder 2, a pressure of about 70 cm3 of the volume of the cavity 4 was set, which
was maintained at 220 °C by an electric cartridge heater of a die 3 for forming molds in
a cylinder with a surface pressure of 0.5 MPa of an air cylinder, kept for 3 minutes, the
water component of the aggregate material mixture was evaporated and caked, and
then the formed mold was taken out from the cavity 4 of the die for forming molds 3.
Then, the formed mold was put in an incubator maintained at 220 °C for 40 minutes,
reacted with cross linking, and then taken out from the incubator. A test of pouring
melted metal was done with this formed mold as a core of the die for casting. An
aluminum alloy was poured at the pouring temperature of 710 °C and no casting
defects occurred. Also, when melted metal was poured at the pouring temperature of
710 ºC, the binders were volatilized and decomposed and the core could be easily
removed after the poured and melted metal was cooled. Also, no discomforting odors
were generated during the forming and pouring, and the odors were like those from
biscuits being baked.
[0051] Example 3
An ethanol-system coating reagent (Threecoat MTS - 720A: Mikawa Kousan Co. Ltd.)
was coated on the mold obtained by the same method for forming to give a core for
casting, and a test of pouring melted metal was carried out. Cast iron (FCD450) was
poured at the pouring temperature of 1370 °C to give an excellent poured and melted
metal without discomforting odors, any casting defects, or generation of deformations.
Also, a core could be easily removed from the poured and melted metal.
[0052] Example 4
Silica sand (Fluttery Sand) of 100 weight parts, polyvinyl alcohol (JP - 05: Nihon
Sakubi - Poval) of 0.2 weight parts, starch (DextrinNSD -1/ Nisshi) of 0.8 weight parts,
citric acid (Fuso Kagaku) of 0.2 weight parts, and water of 5 weight parts, were mixed
with stirring, foamed at about 200 rpm for about 3 minutes by a mixer (Aikousha
Desktop Mixer) (hereafter, the explanation refers to Figure 2) about 90 g of the
aggregate material mixture was put in the cylinder 2, a pressure of about 80 cm3 of the
volume of the cavity 4 was set, which was maintained at 220 - 270 °C by an electric
cartridge heater of a die 3 for forming molds in a cylinder with a surface pressure of 0.5
MPa of an air cylinder, kept for 1 - 3 minutes, the water component of the aggregate
material mixture was evaporated and caked, and then the formed mold was taken out
from the cavity 4 of the die for forming molds 3. Test templates (10 X 10 x L60) were
made from this formed mold and the results measured of the packing densities and the
flexural strength of the test templates kept in the incubator under a humidity of 30%.
The test templates kept in the incubator under a humidity of 98% for 24 hours are
shown in Table 2.
[0053] It is found from Table 2 that the strength in regards to the flexural strength of
the formed molds kept in the incubator under a humidity of 30% for 24 hours is assured
under the conditions of Table 2 to be used for molds. However, at the die temperature of
220 °C, the strength under a humidity of 98% after 24 hours is low even for the
retention time in the die of 3 minutes. Since the cross linking reaction is not sufficient
in the die under this condition, it is necessary to treat the mold with cross linking under
a temperature of 220 °C for about 20 minutes, or under a temperature of 250 °C for
about 10 minutes after taking out the die.
[0054] When the temperature of the die is 250 - 270 °C, the strength after 24 hours at a
humidity of 98% for the retention time in the die of 1 minute is sufficient for use as
molds, so no cross linking treatment after taking a mold from the die is necessary.
[0055] Example 5
Silica sand (Fluttery Sand) of 100 weight parts, polyvinyl alcohol (JP - 05:
manufactured by Nihon Sakubi - Poval) of 0.3 weight parts, sugar (manufactured by
Fuji Nihon Seito) of 1.0 - 2.0 weight parts, citric acid (manufactured by Fuso Kagaku) of
0.4 - 1.2 weight parts, and water of 5 weight parts, were mixed with stirring, foamed at
about 200 rpm for about 3 minutes by a mixer (Desktop Mixer manufactured by
Aikousha) (hereafter, the explanation refers to Figure l), about 90 g of the aggregate
material mixture was put in the cylinder 2, a pressure of about 80 cm3 of the volume of
the cavity 4 was set, which was maintained at 250 °C by an electric cartridge heater of
a die 3 for forming molds in a cylinder with a surface pressure of 0.5 MPa of an air
cylinder, kept for 1 - 3 minutes, the water component of the aggregate material mixture
was evaporated and caked, and then the formed mold was taken out from the cavity 4 of
the die for forming molds 3. Test templates (10 X10 X L60) were made from this formed
mold and the results measured of the packing densities and the flexural strength of the
test templates kept in the incubator under a humidity of 30% for 24 hours are shown in
Table 3.
[0056] Example 6
Silica sand (Fluttery Sand) of 100 weight parts, polyvinyl alcohol (JP - 05:
manufactured by Nihon Sakubi - Poval) of 0.2 weight parts, starch (Dextrin NSD - 100:
manufactured by Nissi) of 0.8 weight parts, and water of 5 weight parts, were mixed
with stirring, foamed at about 200 rpm for about 3 minutes by a mixer (Desktop Mixer
manufactured by Aikousha) (hereafter, the explanation refers to Figure 2), about 90 g of
the aggregate material mixture was put in the cylinder 2, a pressure of about 80 cm3 of
the volume of the cavity 4 was set, which was maintained at 220 °C by an electric
cartridge heater of a die 3 for forming molds in a cylinder with a surface pressure of 0.5
MPa of an air cylinder, kept for 3 minutes, the water component of the aggregate
material mixture was evaporated and caked, and then the formed mold was taken out
from the cavity 4 of the die for forming molds 3. Test templates (10 X10 X L60) were
made from this formed mold and the results measured of the packing densities and the
flexural strength of the test templates kept in the incubator under a humidity of 30%
and the test templates kept in the incubator under a humidity of 98% for 24 hours are
shown in Table 4.
[0057] It is found from Table 4 that the strength in regards to the flexural strengths of
the formed molds kept in the incubator under a humidity of 30% for 24 hours are
assured under the conditions of Table 1, to be used for molds. It is found that the
strengths in regards to the flexural strength of the formed molds kept in the incubator
under a humidity of 98% for 24 hours by adding cross linking agents are assured
sufficiently to be used for molds.
[0058] Example 7
Silica sand (Fluttery Sand) of 100 weight parts, saponin (reagent: manufactured by
Kishida Kagaku) of 0.2 weight parts, starch (Dextrin NSD - L: manufactured by Nissi)
of 0.8 weight parts, citric acid (manufactured by Fuso Kagaku) of 0.4 weight parts, and
water of 6 weight parts, were mixed with stirring, foamed at about 200 rpm for about 3
minutes by a mixer (Desktop Mixer, manufactured by Aikousha) (hereafter, the
explanation refers to Figure 2), about 90 g of the aggregate material mixture was put in
the cylinder 2, a pressure of about 80 cm3 of the volume of the cavity 4 was set, which
was maintained at 250 °C by an electric cartridge heater of a die 3 for forming molds in
a cylinder with a surface pressure of 0.5 MPa of an air cylinder, kept for 2 minutes, the
water component of the aggregate material mixture was evaporated and caked, and
then the formed mold was taken out from the cavity 4 of the die for forming molds 3.
Test templates (10 X 10 X L60) were made from this formed mold and the results
measured of the packing densities and of the flexural strength of the test templates kept
in the incubator under a humidity of 30%. The test templates kept in the incubator
under a humidity of 98% for 24 hours are shown in Table 5.
[0059] It is seen from Table 2 that the strength in regards to the flexural strength of the
formed molds kept in the incubator under a humidity of 30% for 24 hours using a
saponin as aqueous binders also definitely have the conditions of tests Nos. 2-5
necessary to be used for molds. However, when the saponin of No. 1 alone was used,
the strength was not more than 1.0 MPa. When cross linking agents were added to the
saponins as Nos. 2 - 5, it was found that a cross linking reaction occurred, and a
strength sufficient to be used under a humidity of 98% after 24 hours was shown.
[0060] Example 8
A mixture of which the ratio of the contents of polyvinyl alcohol (JP - 05: manufactured
by Nihon Sakubi - Poval), starch (DextrinND - S: manufactured by Nisshi) , and citric
acid (Fuso Kagaku) was 1:4:2 was put in an incubator for 10 minutes. The mixture
when taken out was left under a helium atmosphere in a heat decomposition oven at
590 *C for 5 seconds. Then gases generated by the heat decomposition were passed
through a column (after being kept at 50 °C for 10 minutes, the temperature was raised
to 240 °C at the rate of 10 °C / min and kept for 15 minutes) and the species of the
gases were analyzed by a mass spectrometer. Figure 3 shows the results of the
analyses of the components of the gases generated from the binders of the present
inventions, by that mass spectrometer. As a result, carbon dioxide, acetic acid, and
furfural were detected (Figure 3).
[0061] Example 9
Silica sand (Fluttery Sand) of 100 weight parts, polyvinyl alcohol (JP - 05:
manufactured by Nihon Sakubi - Poval) of 0.2 weight parts, starch (Dextrin NSD - L:
manufactured by Nissi) of 0.8 weight parts, citric acid (manufactured by Fuso Kagaku)
of 0.4 weight parts, and water of 5 weight parts, were mixed with stirring, foamed at
about 200 rpm for about 3 minutes by a mixer (Desktop Mixer, manufactured by
Aikousha) (hereafter, the explanation refers to Figure 1), about 90 g of the aggregate
material mixture was put in the cylinder 2, a pressure of about 80 cm3 of the volume of
the cavity 4 was set, which was maintained at 250 °C by an electric cartridge heater of
a die 3 for forming molds in a cylinder at a surface pressure of 0.5 MPa of an air cylinder,
kept for 2 minutes, and the water component of the aggregate material mixture was
evaporated, caked, and reacted with cross linking and then the formed mold was taken
out from the cavity 4 of the die for molding the molds 3. Test templates (10 X 10 X L60)
were made from this formed mold. The results of the measurements of the bulk
density and the amount of binders of each part are shown in Table 6.
[0062] It is found that the core of a mold (4-5 mm from surface) is low in bulk density
and small in the amount of binders compared to the surface (0—1 mm from the surface).
[0063] Industrial Applicability
At the stage of pouring melted metal of the processes of the forming and casting,
excellent effects are accomplished in that few toxic gases are generated, the formed
molds can be easily removed from poured and melted metal after the pouring, and the
ability to fill the die for forming molds is good. Further, anti-humidity can be
accomplished by a cross linking of the aqueous binders and by cross linking agents.
WE CLAIM :
1. A method of forming molds comprising:
(a) a process of foaming an aggregate material mixture by stirring the
aggregate material mixture containing granular aggregate materials such as
herein described, one or more kinds of aqueous binders, and water;
(b) a process of filling the foamed aggregate material mixture in a
space for forming molds;
(c) a process of caking the aggregate material mixture by evaporating
a water component of the filled aggregate material mixture and forming a mold;
and
(d) a process of taking out the formed mold from the space for forming
molds;
wherein the aqueous binders are selected from the group consisting of the
combination of polyvinyl alcohol or its derivatives and starch or its derivatives,
the combination of saponins and starch or its derivatives, and the combination of
polyvinyl alcohol or its derivatives, and other saccharides.
2. A method of forming molds comprising:
(a) a process of foaming an aggregate material mixture by stirring the
aggregate material mixture containing granular aggregate materials such as
herein described, one or more kinds of aqueous binders, a cross linking agent
which induces a cross linking reaction with the aqueous binders, and water;
(b) a process of filling the foamed aggregate material mixture in a
space for forming molds;
(c) a process of caking the aggregate material mixture by evaporating
a water component of the filled aggregate material mixture and forming molds,
carrying out a cross linking reaction of the aqueous binders and the cross linking
agent; and

(d) a process of taking out the formed mold from the space for forming
molds;
wherein the aqueous binders are selected from the group consisting of the
combination of polyvinyl alcohol or its derivatives and starch or its derivatives,
the combination of saponins and starch or its derivatives, and the combination of
polyvinyl alcohol or its derivatives, and other saccharides.
3. A method of forming molds comprising:
(a) a process of foaming an aggregate material mixture by stirring the
aggregate material mixture containing granular aggregate materials such as
herein described, one or more kinds of aqueous binders, and water
(b) a process of filling the foamed aggregate material mixture in a
space for forming molds;
(c) a process of caking the aggregate material mixture by evaporating
a water component of the filled aggregate material mixture and forming a mold;
(d) a process of taking out the formed mold from the space for forming
molds; and
(e) a process of carrying out a cross linking reaction of the aqueous
binders and the cross linking agent;
wherein the aqueous binders are selected from the group consisting of the
combination of polyvinyl alcohol or its derivatives and starch or its derivatives.
the combination of saponins and starch or its derivatives, and the combination of
polyvinyl alcohol or its derivatives, and other saccharides.
4. The method for forming molds as claimed in any one of claims 1 to 3,
wherein the foamed aggregate material mixture is foamed to be a whipped
cream in which the granular aggregate materials are equally dispersed.
5. The method for forming molds as claimed in any one of claims 1 to 4,
wherein the foamed aggregate material mixture has the ratio of foaming of 50-
80%.
6. The method for forming molds as claimed in any one of claims 1 to 5,
wherein the formed aggregate material mixture is filled in a space for forming
molds by directly pressurizing by the press fitting of a piston in a cylinder in
process (b).
7. The method for forming molds as claimed in any one of claims 1 to 5,
wherein the formed aggregate material mixture is filled in a space for forming
molds by providing compressed air to a cylinder in the process (b).
8. The method for forming molds as claimed in any one of claims 1 to 7,
wherein the water component of the filled aggregate material mixture is
evaporated by the heat of the heated die in process (c).
9. The method for forming molds as claimed in any one of claims 1 to 8,
wherein the bubbles dispersed in the aggregate material mixture and the water in
the aqueous binders gather in the central part of the mold by the evaporation of
the water component of the filled aggregate material mixture to form a mold
having a low packing density in its central part in the process (c).
10. The method for forming molds as claimed in any one of claims 1 to 9,
wherein the aqueous binders are soluble in water at ordinary temperature.
11. The method for forming molds as claimed in any one of claims 1 to 10,
wherein at least one kind of the aqueous binders is foarnable.

12. The method for forming molds as claimed in any one of claims 1 to 11,
wherein 0.1-5.0 weight parts of the aqueous binders in relation to the granular
aggregate materials are contained.
13. The method for forming molds as claimed in any one of claims 2 to 12,
wherein the cross linking agent is selected from compounds having carboxyl
groups.
14. The method for forming molds as claimed in claim 13, wherein the
compound having carboxyl groups is selected from the group consisting of oxalic
acid, maleic acid, succinic acid, citric acid, butanetetracarboxylic acid, methyl-
vinyl ether - maleic anhydride coploymers, and isobutylene - maleic anhydride
coploymers.
15. The method for forming molds as claimed in any of claims 13 or 14,
wherein the amount added of the cross linking agent is at least 5 weight % in
relation to the aqueous binders.
16. A core for casting metal produced by the method for forming molds as
claimed in any one of claims 1 to 15.
17. The core for casting metal as claimed in claim 16, wherein the amount of
aqueous binders of the central part thereof is less than that of the surface part.
18. The core for casting metal as claimed in claim 16, wherein the central core
is used for casting a non-ferrous alloy.
19. The core for casting metal as claimed in claim 18, wherein the casting
non-ferrous alloy is aluminum alloy or a magnesium alloy.
A method of forming a mold which scarcely emits any gas having a
harmful effect on human body even upon binder heating; and a core for metal
casting are disclosed. More particularly, there is provided a method of forming a
mold which comprise agitating an aggregate mixture composed of granular
aggregate, a water soluble binder and water so as to foam the aggregate
mixture, charging the foamed aggregate mixture in a space for mold formation
and evaporating water to thereby solidify the aggregate mixture, and there is
further provided a core for metal casting. In one embodiment, a cross linking
agent can be added so that curing can be effected before or after taking our of
the mold from the space for mold formation.


A method of forming a mold which scarcely emits any gas having a
harmful effect on human body even upon binder heating; and a core for metal
casting are disclosed. More particularly, there is provided a method of forming a
mold which comprise agitating an aggregate mixture composed of granular
aggregate, a water soluble binder and water so as to foam the aggregate
mixture, charging the foamed aggregate mixture in a space for mold formation
and evaporating water to thereby solidify the aggregate mixture, and there is
further provided a core for metal casting. In one embodiment, a cross linking
agent can be added so that curing can be effected before or after taking our of
the mold from the space for mold formation.


A method of forming a mold which scarcely emits any gas having a
harmful effect on human body even upon binder heating; and a core for metal
casting are disclosed. More particularly, there is provided a method of forming a
mold which comprise agitating an aggregate mixture composed of granular
aggregate, a water soluble binder and water so as to foam the aggregate
mixture, charging the foamed aggregate mixture in a space for mold formation
and evaporating water to thereby solidify the aggregate mixture, and there is
further provided a core for metal casting. In one embodiment, a cross linking
agent can be added so that curing can be effected before or after taking our of
the mold from the space for mold formation.


Documents:

500-KOLNP-2006-CORRESPONDENCE 1.1.pdf

500-KOLNP-2006-CORRESPONDENCE.pdf

500-KOLNP-2006-FORM 27 1.1.pdf

500-KOLNP-2006-FORM 27.pdf

500-KOLNP-2006-FORM-27.pdf

500-kolnp-2006-granted-abstract.pdf

500-kolnp-2006-granted-assignment.pdf

500-kolnp-2006-granted-claims.pdf

500-kolnp-2006-granted-correspondence.pdf

500-kolnp-2006-granted-description (complete).pdf

500-kolnp-2006-granted-drawings.pdf

500-kolnp-2006-granted-examination report.pdf

500-kolnp-2006-granted-form 1.pdf

500-kolnp-2006-granted-form 18.pdf

500-kolnp-2006-granted-form 3.pdf

500-kolnp-2006-granted-form 5.pdf

500-kolnp-2006-granted-gpa.pdf

500-kolnp-2006-granted-reply to examination report.pdf

500-kolnp-2006-granted-specification.pdf


Patent Number 233927
Indian Patent Application Number 500/KOLNP/2006
PG Journal Number 17/2009
Publication Date 24-Apr-2009
Grant Date 22-Apr-2009
Date of Filing 03-Mar-2006
Name of Patentee SINTOKOGIO, LTD.
Applicant Address 28-12, MEIEKI 3-CHOME, NAKAMURA-KU, NAGOYA-SHI, AICHI-KEN
Inventors:
# Inventor's Name Inventor's Address
1 ZENPO, TOSHIHIKO C/O. SINTOKOGIO, LTD. TOYOKAWA SEISKUSHO 1 HONOHARA, 3-CHOME, TOYOKAWA-SHI, AICHI-KEN
2 KATO, YUSUKE C/O. SINTOKOGIO, LTD. TOYOKAWA SEISKUSHO 1 HONOHARA, 3-CHOME, TOYOKAWA-SHI, AICHI-KEN
3 ASANO, NORIHIRO C/O. SINTOKOGIO, LTD. TOYOKAWA SEISKUSHO 1 HONOHARA, 3-CHOME, TOYOKAWA-SHI, AICHI-KEN
4 NAGASAKA, MASAHIKO C/O. SINTOKOGIO, LTD. TOYOKAWA SEISKUSHO 1 HONOHARA, 3-CHOME, TOYOKAWA-SHI, AICHI-KEN
5 NISHIKAWA, KAZUYUKI C/O. SINTOKOGIO, LTD. TOYOKAWA SEISKUSHO 1 HONOHARA, 3-CHOME, TOYOKAWA-SHI, AICHI-KEN
PCT International Classification Number B22C 1/00,B22C 1/26
PCT International Application Number PCT/JP2004/012553
PCT International Filing date 2004-08-31
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2003-309473 2003-09-02 Japan
2 2004-101685 2004-03-31 Japan
3 2004-137791 2004-05-06 Japan